In a combined read/write head (merged, "Piggyback", or types yet to be devised) using modem spin valve technology for the read head, it is necessary to pin a pinned layer of material in the read head after the entire head is assembled. The magnetization of the ferromagnetic pinned layer is pinned perpendicular to the air bearing surface. Most common method of pinning is by exchange pinning the ferromagnetic layer to an antiferromagnetic layer. This requires setting the pinned layer at an elevated temperature, above the blocking temperature of the antiferromagnet, in a magnetic field oriented perpendicular to the air bearing surface. For some antiferromagnetic systems, like NiMn, high temperature (250.degree. C.) annealing may be required in a field oriented perpendicular to the ABS.
Unfortunately, the write head poles (P1 and P2) can be negatively impacted by exposure to such high temperatures. The annealing of the P1/P2 materials in a field oriented perpendicular to the ABS may induce a magnetic easy axis perpendicular to the ABS in the P1/P2 layers. The magnetic easy axis perpendicular to the ABS is not desirable for high frequency operation of the write head. Furthermore, such domains in the P1 layer is likely to negatively effect the operation of the adjacent read head.
Since the preferred construction for the read head appears to include the high temperature reset discussed above, it would be desirable to find some way to prevent the negative effects on the write poles which must be subjected to the same high temperature. However, to the inventor's knowledge no effective means or method for accomplishing this has existed in the prior art.